Summary:
In the light of the multiple exploded planet hypothesis, evidence in this book
that Mercury, Mars, and Pluto are escaped moons rather than original major
planets, and the arguments in Chapter 19 in favor of a solar fission origin for
the major planets, we re-visit the original solar system. We take note of the
six original major planets to occur in "twin" pairs, and of the main
asteroid belt and new trans-Neptunian belt to apparently each have two parent
bodies as well. If fission is considered as the principal mechanism for all
major planet and natural moon formation, then solid planets will tend to form
with singlet moons, whereas gaseous parent bodies (including the Sun) will
tend to fission off smaller bodies (moons) in nearly-twin pairs. We examine
the theory of formation by fission and compare it to the major planets and
large, natural moons of the solar system. A very good match is found,
including the surprising fulfillment of a prediction of the model regarding
the order of the pairings in a previously unrecognized pattern. Using a Titius-Bode
law for planetary spacing in its simplest form (where each planet has double
the period of the previous one), we infer the existence of twelve original major planets,
of which half remain today. Two short-lived gas giant planets may be
responsible for the "late heavy bombardment" episode in the early
solar system, and for building up the mass of Jupiter.

Introduction

The
solar system presently consists of nine known planets. But the distinction
between "planet," "moon," "asteroid," and
"comet" is somewhat arbitrary, being based mainly on broad, general
appearance. For each category, marginal cases exist that can be argued either
way. For example, Pluto is sometimes said to be too small to be a major
planet. It was suggested in Chapter 17 that Pluto would be more properly
classified as a former moon of Neptune,[183]
as a large asteroid, or even as a comet. Indeed, Pluto would probably sprout a
coma and tail if it were brought considerably closer to the Sun.

In
the inner solar system, Mercury is very likely to be an escaped moon of Venus,
a thesis for which a great deal of evidence exists (see Chapter 13). In
Chapter 24, the author suggested that Mars is a former moon of “Planet
V," the original planet next out from the Earth. Although none of these
suggestions can yet be proved, considerable evidence can be brought to bear in
support of each case.

If
we accept these tentative identifications and exclude the three smallest
planetary bodies from consideration, it is interesting to look at what is left
by way of true, major planets in the original solar system. First we have
Venus and Earth, both rather similar in mass, composition, solar distance, and
number of original significant moons (if our premise about Mercury is
correct). Following the asteroidal gap, we have the two largest gas giants,
Jupiter and Saturn, likewise with similar composition and numerous moons, and
with masses and solar distances more similar to one another than to any other
planet. Next out we have another pair of twins, Uranus and Neptune, with
similar masses, compositions, and solar distances. Their number of original
significant moons would likewise have been similar if the conjecture about
Pluto and Charon’s origin as former Neptunian moons is correct.

One
aspect of this picture is striking: a tendency for these planets to occur in
pairs. Two of these pairs are similar enough for the respective planets to
occasionally be called “twins." Jupiter and Saturn might well be called
“twins” too if Jupiter were a bit less massive and Saturn lacked its
beautiful rings. But the rings of Saturn are almost certainly a recent
addition to that planet (Kerr, 1996).[184]
And as we will see, there is reason to suspect that Jupiter had considerably
less mass at the outset than it now does.

Each
pair is notably dissimilar to its adjoining pair or pairs. Now there is no
particular reason under the “primeval solar nebula” hypothesis of
planetary formation why this should be so. The nebula from which the planets
allegedly condensed should have been rather homogeneous in most respects, and
planet masses should have had a smooth radial gradient with solar distance.

On
the other hand, Chapter 19 argued that origin of planets by fission from the
Sun should be reconsidered because it elegantly solves several problems the
standard model does not. For example, if planets fission from the Sun due to
overspin while the Sun is still accreting, this more easily explains how 98%
of the solar system’s angular momentum ended up in the planets. That fact
has always been considered significant for understanding solar system
formation since all the planets combined have less than 0.002 of the mass of
the Sun.

The
fission hypothesis would also solve the mystery of the dominance of prograde
rotation for these original planets, since they would have shared in the
Sun’s prograde rotation at the outset. J.J. Lissauer[185]
summarizes the latest results on this puzzle for the standard model: “Almost
all the previous calculations were wrong … If you accrete planets from a
uniform disk of planetesimals, the observed prograde rotation just can’t be
explained.”

The
Fission Theory for the Origin of Planets and Moons

There
are some basic similarities between the solar fission hypothesis for origin of
the planets and the more traditional theory of accretion from the primeval
solar nebula. In both cases, an extended cloud of gas and dust contracts, with
a concentration toward the center eventually becoming dense and hot enough to
be classified as a star. Once that happens, the extended cloud of gas and
dust, stabilized in size, forms a rapidly rotating disk outside the parts of
the proto-Sun where nuclear fusion is taking place. The core collapses
gravitationally from the inside out, with internal heat stabilizing the
configuration. The disk will tend to continually spin up the central star. But
the central star cannot continue to accrete matter from the rapidly rotating
disk without flinging a significant fraction of it back out. The mechanism for
that is still debated, with some astronomers favoring polar outflow models and
others favoring outflows that originate in the nebular disk.[186]

However,
it would be incorrect to think of the disk as comprised of numerous discrete
globules that can collide and accrete, as the solar nebula hypothesis
requires. Recall that two bodies in similar orbits around a central mass will
go into a state of libration and avoid collisions. (See Chapter 6.) The Trojan
asteroids in Jupiter’s orbit, for example, always avoid collision with
Jupiter by librating. The more similar the orbits any two bodies have, the
more nearly impossible collision between them becomes.

Meanwhile,
the core of the proto-Sun has no such problems accreting mass from the disk
through collisions and steadily growing in mass and size. And there is a more
natural way for the planet formation process to proceed from there. The
spin-up of the proto-Sun will make it first oblate, then prolate as it
approaches an overspin state where centrifugal forces exceed gravitational
forces. This shape is called a “Maclaurin spheroid." When the star-disk
boundary reaches the overspin condition, the two prolate bulges on opposite
sides of the proto-Sun break away and form twin proto-planets in low orbits
just above the proto-star surface in the inner disk. This tendency to form
planets in twin (although generally not identical) pairs is the reason we have
chosen to revisit this model in this chapter.

Artist's concept of
planetary fission. Click here to view a
short animation (419KB).

The
remainder of the process is similar to the proposed formation of the Moon by
fission from an over-spinning Earth. (Chapter 14. See Binder, 1984 for a
diagram and description of this process as it applies to the fission of the
Moon.[187])
The initial spin of the proto-planets, as well as their orbits, would be that
of the surface of the proto-Sun, and therefore always prograde. Subsequent
tidal evolution will evolve the twin proto-planets outward at slightly
different rates, with the more massive of the two evolving outward faster
because its tidal forces are stronger. Although such tidal forces are
negligible in the solar system today, they would have been substantial during
the formation stages for the Sun, called its “T Tauri” phase. (Note: Each
doubling of the solar radius increases such tidal forces by roughly two orders
of magnitude.) Such orbital evolution is very similar to that of Mercury
relative to Venus following the inferred tidal escape of the former from the
latter (see Chapter 13).

Evolution
of the planets would typically proceed via tides and drag toward the
maximum-stability Titius-Bode-Law configuration, wherein each planet has a
circular, co-planar orbit with double the orbital period of the next planet
in. Once that was achieved, further orbital evolution would cease. All the
major features of the planetary system can apparently be derived from the
process just outlined, although it is different in important ways from the
standard solar nebula picture.

Satellite
Formation

Some
special cases need to be considered further. First consider the case that the
rotating body is solid or has substantial material strength, as for the
Earth-Moon system. Then just the weaker of the two globules at either end of
the prolate major axis would fission, and the rest of the body would snap back
to a smaller, rounder shape with a slower spin. After all, the spinning body
has given away a substantial part of its angular momentum to the fissioned
globule. So only a single moon results. This would apparently be generally
true – gaseous or liquid parent bodies would produce pairs of moons by
fissioning, whereas solid bodies would produce singlet moons.

It is usually objected that tidal friction between a proto-planet and a
gaseous parent, such as the proto-Sun, ought to be negligible because the
gaseous parent can reshape itself so that any tidal bulge has no lag or lead,
and therefore transfers no angular momentum to the proto-planet. This argues
that frictional forces between Sun and proto-planet will always be negligible,
so no significant orbital evolution will take place. However, as explained in
Chapter 6, it is not the usual longitudinal tidal forces that are effective in
this case, but rather radial tidal forces. The proto-planet causes the
proto-Sun to bulge radially outward. But the proto-Sun is rotating
differentially with depth, slower toward the center and faster toward the
surface, as we saw above. So as the proto-Sun bulges, part of its mass is
raised into a layer with faster rotation, thereby causing a leading tidal
bulge that would cause the proto-planet that raised it to evolve outward.

Now consider a gaseous proto-planet. It will cool and contract rapidly
once away from the proto-Sun. And as it does so, it too will acquire
differential rotation, but with the fastest rotation toward its core and the
slowest rotation toward its surface – the opposite of the rotation gradient
for the proto-Sun. As the proto-planet contracts, it must spin up to conserve
angular momentum, so it too can reach an overspin condition. Being gaseous, a
pair of moons will be spawned by the fission process. But unlike the solar
case, the differential rotation of the parent will cause a tidal bulge lag,
which will cause the moons to lose angular momentum and spiral slowly inward.

We are safe in presuming that the parent planet will contract faster
from cooling than the tidal forces can operate to bring moons down. If that
were not the case, no moons would be likely to survive. The observable major
difference this causes with the planet case is that the more massive of any
pair of moons should evolve inward faster. For planets, as we saw earlier, the
more massive member of each pair should be the outer one.

Application
to Planet Formation

It
will now be apparent why the appearance of the solar system’s major planets
in matching pairs is significant. That fact strongly favors a fission origin
over a traditional solar nebula origin. But after each planet pair is formed
in this way, it will be some time before the Sun and extended cloud reach
another overspin as they continue to contract. By that time the Sun will be
hotter and more massive and the extended cloud smaller. So the next pair of
planets will fission under rather different conditions, forming another pair
of planets similar to one another but dissimilar from all previous pairs.

That is the theory. How does it compare to reality in the solar system?
The Venus-Earth and Uranus-Neptune pairs conform to expectations, assuming
that some later event tilted the spin axis of Uranus. The more massive planet
in each of these “twin” pairs is the outer one, as the theory requires.
However, the Jupiter-Saturn pair has the more massive planet (Jupiter) closer
to the Sun. Indeed, Jupiter is roughly three times more massive than Saturn,
which brings into question whether it may be considered a “twin” at all.

The next area of attention is the large gap between Mars and Jupiter.
Readers will by now be familiar with the exploded planet hypothesis, and its
inference that two major planets exploded there during the past half billion
years. Of these two, “Planet K” in the main asteroid belt was surely the
larger, giving rise to C-type asteroids which apparently comprise 80% of all
main-belt asteroids. “Planet V” was apparently located roughly where the
orbit of Mars is now, and was the parent of Mars prior to its explosion, as
well as the source for S-type asteroids.

The two planets hypothesized to have exosted and exploded in that gap,
K and V, might be considered another pair of “twins." The more massive
of the two is the outermost, as expected by the fission theory. And the two
are certainly alike in that they both exploded after roughly four billion
years of evolution. Beyond that, we can say little except that most of their
mass would have been vaporized by the explosion, and almost all of it that did
not escape the solar system would have been swept up by Jupiter. Solar wind
and radiation pressure would have ensured that all vaporized material would be
driven toward Jupiter until it was swept up by that gas giant planet. So this
scenario implies that Jupiter’s mass has been increased from its original
value by some unknown but significant amount. This apparent fact makes us
pause to consider whether we must regard Jupiter as a contradiction of the
fission theory simply because its mass is larger than Saturn’s. Perhaps its
original mass was smaller than Saturn’s. Among the supporting evidence for
this conjecture we find suggestions that Jupiter’s mass has apparently
increased by roughly 40% just since its asteroidal moons were captured,
probably within the last billion years.[188]

However, we note that hypothetical Planets K and V were terrestrial planets, judging
from the asteroids from them that we observe today. That fact implies
generally smaller masses, probably in the 4-10 Earth-mass range. Had they been
substantially larger, they would surely have been gas giants without a solid
surface capable of producing asteroids. So using our best inference, there is
insufficient mass in planets K and V to account for Jupiter’s apparent
excess mass under the fission theory.

But that presents a new challenge. There is apparently a huge mass
difference between Planet K (perhaps 10 Earth masses) and Jupiter (318 Earth
masses). Such a large mass discontinuity would be unexpected in most formation
theories, and would seem to require some ad hoc mechanism to explain it. The
only alternative is to conjecture that another planet formerly existed between
Planet K and Jupiter to provide an intermediate mass stage of planet
formation. That planet (or planet pair, if we are guided by the fission
theory), like Planets K and V, may have exploded, completely vaporizing in the
process. If that explosion were early enough in the solar system’s history,
the gap left behind could have been closed by tidal and drag evolution of the
remaining planets, since these processes were still occurring in the early
solar system.

In support of this conjecture, we offer two additional lines of
evidence. The first is direct evidence for the explosion of one or more very
large planets in the very early solar system. From studies of lunar rocks
it is now known that the Moon, and presumably the entire solar system with it,
underwent a “late heavy bombardment” of unknown origin not long after the
major planets formed. The following are relevant descriptions of the event:[189]

“[The
late heavy bombardment] occurs relatively late in the accretionary history of
the terrestrial planets, at a time when the vast majority of that zone’s
planetesimals are already expected to have either impacted on the
protoplanets, or been dynamically ejected from the inner planets region.”

“It appears that a flux of impactors flooded the terrestrial planets region at
this point in the solar system’s history, and is preserved in the cratering
record of the heavily cratered terrain on each planet.”

“An
essential requirement of any explanation for the late heavy bombardment is
that the impactors be ‘stored’ somewhere in the solar system until they
are suddenly unleashed about 4.0 Gyr ago.”

“A
plausible explanation for the late heavy bombardment remains something of a
mystery.”

“...it
seems likely that the late heavy bombardment is not the tail-off of planetary
accretion but rather is a late pulse superimposed on the tail-off. Nor is
there any reason to suppose that it was the only such pulse; it may have been
preceded by several others which are not easily discernible from it in the
cratering record.”

In
short, the late heavy bombardment, a real solar system event, sounds like just
the sort of early planetary explosion event that is suggested by the line of
conjecture we were pursuing.

A second, somewhat weaker, line of evidence arises from use of the
dynamical constraint that the most stable orbital configuration is the 2-to-1
resonance. If the solar system originally evolved to such a configuration
wherein each planet had half the orbital period of the next planet out, then
there appears to be room for one or two additional planets that may no longer
exist. In particular, if we assume that Venus must have originated at least as
close to the Sun as Mercury is now, as indicated by the Van Flandern and
Harrington scenario (Chapter 13), there is room for precisely two additional
planets between Earth and Uranus. At least one of those planets, perhaps both,
was surely in the zone between Planet K and Jupiter, and was responsible for
major accretion of mass in Jupiter. We designate this hypothetical body as
“Planet A."

We will then call the other hypothetical body “Planet B." It may
have been the “twin” of Planet A, also located just inside Jupiter’s
orbit, in which case Jupiter was originally much smaller and was Saturn’s
twin counterpart. We call this possibility “Planet B1." Or it may have
been Saturn’s twin, located between Jupiter and Saturn in a region were
comets often have outbursts, which suggests impacts by numerous small
planetesimals in that region. We call this latter possibility “Planet
B2," which would imply that Jupiter was Planet A’s twin.

A summary of these conjectured original planets is shown in
Table
1,
which adopts the first possibility for Planet B.

Planet

Original
Distance (au)

Recent
Distance
(au)

Original
Period
(yr)

Original
Mass
(x Å)

Present
Mass
(x Å)

Venus

0.5

0.7

0.35

0.8

0.82

Earth (x Å)

0.8

1.0

0.7

1.0

1.00

V

1.3

1.6

1.4

8

---

K

2.0

2.8

2.8

10

---

A

3.2

---

5.6

120

---

B

5.0

---

11

150

---

Jupiter

7.9

5.2

22

65

318

Saturn

13

9.5

45

80

95

Uranus

20

19.2

90

14

14.6

Neptune

32

30.0

180

17

17.3

T

50

---

360

2

---

X

80

---

720

3

---

Table 1. The Original
solar system as inferred from the planetary fission theory. Original periods
all have 2-to-1 ratios. [revised 2004/03/15 to reflect new
information about trans-Neptunian objects, and that "Planet X" is a suitable
parent for the TNO named Sedna]

Looking beyond Neptune, we note what may be another asteroid belt,
possibly the remnants of an exploded planet in the outer solar system, in the
form of tens of thousands of large fragments in Pluto-like orbits. This is
often referred to as the “Kuiper Belt," although it apparently has
little or nothing to do with the comets that either Kuiper or more recent
astronomers predicted. We designate the hypothetical original
parent planet as “Planet T," since we prefer to call the asteroids in
that region TNOs (for Trans-Neptunian Objects).

That
leaves the hypothetical Planet X (Chapter 18), the source of unmodeled
perturbations on outer planets and certain comets, still undiscovered. We are
of course free to presume that T and X were likewise twins at the outset,
although we have no means yet to verify that presumption. But it would fill
out the original solar system to the distance beyond which passing stars would
make planet orbits unstable in the long run.

Of
course, it should be noted here that Planet X may now itself be an asteroid
belt, long since exploded. The perturbations in the outer planets and comets
were mildly inconsistent with a single perturbing ring. But as we have
remarked on earlier occasions, if there is more than one significant cause of
the remaining perturbations, such as two rings, sorting that out by dynamical
analysis of the observations alone will not succeed. If Planet X is now
exploded, then the T and X pair would apparently be similar to the V and K
pair. They would have produced two overlapping asteroid belts with presumably
compositionally distinct asteroids, similar to the S-type and C-type asteroids
in the inner and outer main asteroid belt. Certainly, the prediction of a
second planetesimal belt beyond Neptune, if fulfilled, would be a strong point
in favor of the fission theory for the origin of planets.

In
summary, our view of the original solar system from the perspective of the
fission theory is rather different from the planetary system we are familiar
with today. We expect that originally there were six pairs of “twin”
planets: Venus/Earth, V/K, A/B, Jupiter/Saturn, Uranus/Neptune, T/X. Or it is
possible that A/Jupiter was a pair, and B2/Saturn was another. It is sobering
to realize that if our deductions are valid, fully half of the solar
system’s original planets may have perished in explosions over the past 4.5
billion years.

The
strong similarity of pair members compared to the differences among pairs
suggests a common origin of pair members. In the solar fission theory, when
the Sun reaches overspin, two planets would form simultaneously on opposite
sides of the Sun. The larger of the two masses would evolve outward by tidal
friction faster than the other, as observed for each pair except
Jupiter/Saturn, where Jupiter is over-massive. But the biggest jump in mass is
at this location too. This may have resulted from a missing pair, both of
which perhaps exploded in the very early solar system, producing the period of
heavy bombardment, and accreting mass to Jupiter. The remnant TNOs and the
hypothetical Planet X may represent yet another pair of original planets.

Application
to Satellite Formation

The theory predicts that planetary moons have originated through the
same process, with the exception that tidal forces would cause moons of gas
giant planets to evolve inward. This predicts that the large, regular moons of
the gas giant planets will occur in pairs, with the more massive always being
the inner of the two. How does that prediction compare to reality? The results
are in Table
2. Taking masses in units of 10-5 of the primary’s mass,
and we include all moons with mass > 1. Distances are in multiples of the
primary’s radius. We have included Pluto and Charon as if the conjecture
that they are escaped former moons of Neptune is true, as proposed in Chapter
17.

The table points up some interesting patterns among these major
planetary satellites. They do indeed tend to occur in pairs, and the inner
member of each pair is always the more massive, just as the fission theory
predicts. This alternating sequence of satellite masses has not been
previously recognized, to this author’s knowledge, much less considered
significant.

Jupiter and Uranus have the most regular and apparently undisturbed
large satellite systems: circular and co-planar orbits, orbit-synchronized
spins, with orbital periods each roughly double that of the next moon in.
Correspondingly, their patterns contain no exceptions to the requirements of
the fission theory. Neptune, of course, has a highly disrupted satellite
system. But the close resemblance between Pluto and Triton has been noted by
many astronomers. They surely qualify as “twins” as well as any pair of
solar system bodies. The fission theory tells us that Pluto (with smaller
mass) must have been exterior to Triton in the original configuration, which
is consistent with results obtained nearly two decades ago and reviewed in
Chapter 17.

Nereid
has only 2% of the mass it would need to qualify as a large satellite by the
criterion adopted here, so it is not a member of a satellite pair with Charon.
Charon’s presumed original partner has most likely been ejected into
independent solar orbit, very much the way Pluto was, where it awaits
discovery as probably the largest of the undiscovered TNOs. Alternatively, it
may have transferred to Planet X.

Among the gas giant planets, Saturn is the main surprise. Its many
moons have rather unevenly spaced orbits with several huge gaps, interspersed
with rings of material. It seemed evident that the Saturnian moons were not in
their original orbits well before this analysis. Now we see yet another
criterion that underscores that disturbed condition: Of Saturn’s eight
original, presumably non-asteroidal moons, only Titan is as large as 10-5
of Saturn’s mass. Titan weighs in at 23.8 x 10-5 Saturn, making
it the most massive moon in the solar system. The next largest Saturnian moon,
Rhea, is roughly 50 times smaller in mass. Most of the others range from a few
times 10-6 to a few times 10-8 of Saturn’s mass. One
is tempted to conjecture about the nature of the disruption event, possibly
including the formation of Saturn’s spectacular icy rings. But it is
difficult to see evidence directing us toward a unique cause.

Conclusion

If we make allowance for special cases that have most probably been
altered from their original condition since the solar system’s beginning, as
judged by lines of evidence existing before this analysis began, we may
conclude that the undisturbed solar system members provide a spectacularly
good match to the predictions of the tidal fission theory. That includes major
planets and large, regular moons.

At one point I began to wonder about the inference in Table
1 that the Earth was much closer to the Sun in the early solar system
than it is now. Would Earth at that distance have been too hot to have oceans?
Then I opened the May 23rd (1997) issue of Science
magazine and found an article on “the early faint Sun paradox," trying
to figure out what kept the Earth from freezing four billion years ago, when
the Sun had 25%-30% less luminosity than it does today (Sagan and Chyba,
1997).[190]
A good theory should always provide pleasant surprises, not new mysteries; and
this one had just produced a very pleasant one--a solution to the early faint
Sun paradox.

But
to be a scientific theory, a model must be falsifiable; and to be useful it
must make successful predictions. So we conclude with an important prediction,
the failure of which will falsify the hypothesis. The astronomy news has been
filled over the past two years with announcements of discoveries of planets
orbiting other stars. The fission theory predicts that such planets will tend
to occur in twin pairs, with some exceptions, as we have seen in our solar
system. However, extra-solar planets cannot be viewed directly, even with the
Hubble Space Telescope. Their existence must be inferred by indirect means,
such as looking for a periodic wobble in the position of a visible parent
star.

If extra-solar planets do occur as twins, that will not be immediately
evident in the earliest observations because it is difficult to separate out
periods for bodies of similar mass that are either close to the same value or
are in resonance with one another. The first data will reveal just a single
member of each pair. Observations over a longer time span will make it appear
that the orbit is highly eccentric, when in reality the wobble of the star
reflects the beating of two near-resonance periods. But with a still longer
time span of data, the dual nature of the planets will be revealed. We predict
that many of the discoveries of extra-solar planets recently announced will
follow that course as the span of observations lengthens in the coming years.